A novel strontium(II)-modified calcium phosphate bone cement stimulates human-bone-marrow-derived mesenchymal stem cell proliferation and osteogenic differentiation in vitro

In the present study, the in vitro effects of novel strontium-modified calcium phosphate bone cements (SrCPCs), prepared using two different approaches on human-bone-marrow-derived mesenchymal stem cells (hMSCs), were evaluated. Strontium ions, known to stimulate bone formation and therefore already used in systemic osteoporosis therapy, were incorporated into a hydroxyapatite-forming calcium phosphate bone cement via two simple approaches: incorporation of strontium carbonate crystals and substitution of Ca²⁺ by Sr²⁺ ions during cement setting. All modified cements released 0.03–0.07 mM Sr²⁺ under in vitro conditions, concentrations that were shown not to impair the proliferation or osteogenic differentiation of hMSCs. Furthermore, strontium modification led to a reduced medium acidification and Ca²⁺ depletion in comparison to the standard calcium phosphate cement. In indirect and direct cell culture experiments with the novel SrCPCs significantly enhanced cell proliferation and differentiation were observed. In conclusion, the SrCPCs described here could be beneficial for the local treatment of defects, especially in the osteoporotic bone.     

Influence of a novel radiopacifier on the properties of an injectable calcium phosphate cement

An injectable calcium phosphate cement (CPC) with excellent radiopacity was proposed by introducing a novel radiopacifier, strontium carbonate, into the powder phase of CPC. The results showed that the cement showed improved radiopacity even when the content of strontium carbonate was only 8 or 12wt.%. The addition of 8 or 12wt.% strontium carbonate clearly improved the injectability and compressive strength of the cement. Furthermore, the addition of strontium carbonate influenced the pore distribution in the cement. An injectable CPC containing 8 or 12wt.% strontium carbonate has the potential for use in procedures such as vertebroplasty and kyphoplasty.     

A novel injectable,cohesive and toughened Si-HPMC (silanized-hydroxypropyl methylcellulose) composite calcium phosphate cement for bone substitution

This study reports on the incorporation of the self-setting polysaccharide derivative hydrogel (silanized-hydroxypropyl methylcellulose, Si-HPMC) into the formulation of calcium phosphate cements (CPCs) to develop a novel injectable material for bone substitution. The effects of Si-HPMC on the handling properties (injectability, cohesion and setting time) and mechanical properties (Young’s modulus, fracture toughness, flexural and compressive strength) of CPCs were systematically studied. It was found that Si-HPMC could endow composite CPC pastes with an appealing rheological behavior at the early stage of setting, promoting its application in open bone cavities. Moreover, Si-HPMC gave the composite CPC good injectability and cohesion, and reduced the setting time. Si-HPMC increased the porosity of CPCs after hardening, especially the macroporosity as a result of entrapped air bubbles; however, it improved, rather than compromised, the mechanical properties of composite CPCs, which demonstrates a strong toughening and strengthening effect. In view of the above, the Si-HPMC composite CPC may be particularly promising as bone substitute material for clinic application.     

Preparation and characterization of a novel strontium-containing calcium phosphate cement with the two-step hydration process

A novel Sr-containing calcium phosphate cement (CPC) with excellent compressive strength, good radiopacity and suitable setting time was developed in this work. The two-step hydration reaction resulted in a high compressive strength, with a maximum of up to 74.9 MPa. Sr was doped into the calcium-deficient hydroxyapatite as a hydrated product during the hydration reaction of the CPC. Because of the existence of Sr element and the compact microstructure after hydration, the Sr-containing CPC shows good radiopacity. It is expected to be used in orthopedic and maxillofacial surgery for bone defects repairing.     

明胶溶胀行为对自固化多孔骨水泥性能和结构的影响

目的 研究明胶溶胀行为对多孔骨水泥性能和结构的影响。方法 在α-磷酸钙骨水泥体系中加入生物明胶，研究明胶对骨水泥水化产物、抗压强度和产物微结构所产生的影响。结果利用明胶的溶胀行为与水化过程中体系pH值变化的相关性，可制备具有大孔和微孔结构的骨水泥。结论加入明胶促进羟基磷灰石的成核，提高骨水泥的抗压强度。     

Bone formation induced by strontium modified calcium phosphate cement in critical-size metaphyseal fracture defects in ovariectomized rats

The first objective was to investigate new bone formation in a critical-size metaphyseal defect in the femur of ovariectomized rats filled with a strontium modified calcium phosphate cement (SrCPC) compared to calcium phosphate cement (CPC) and empty defects. Second, detection of strontium release from the materials as well as calcium and collagen mass distribution in the fracture defect should be targeted by time of flight secondary ion mass spectrometry (TOF-SIMS). 45 female Sprague–Dawley rats were randomly assigned to three different treatment groups: (1) SrCPC (n = 15), (2) CPC (n = 15), and (3) empty defect (n = 15). Bilateral ovariectomy was performed and three months after multi-deficient diet, the left femur of all animals underwent a 4 mm wedge-shaped metaphyseal osteotomy that was internally fixed with a T-shaped plate. The defect was then either filled with SrCPC or CPC or was left empty. After 6 weeks, histomorphometric analysis showed a statistically significant increase in bone formation of SrCPC compared to CPC (p = 0.005) and the empty defect (p = 0.002) in the former fracture defect zone. Furthermore, there was a statistically significant higher bone formation at the tissue–implant interface in the SrCPC group compared to the CPC group (p < 0.0001). These data were confirmed by immunohistochemistry revealing an increase in bone-morphogenic protein 2, osteocalcin and osteoprotegerin expression and a statistically significant higher gene expression of alkaline phosphatase, collagen10a1 and osteocalcin in the SrCPC group compared to CPC. TOF-SIMS analysis showed a high release of Sr from the SrCPC into the interface region in this area compared to CPC suggesting that improved bone formation is attributable to the released Sr from the SrCPC.     

Mechanical testing and osteointegration of titanium implant with calcium phosphate bone cement and autograft alternatives

The purpose of this study was to evaluate the osteointegration of a titanium (Ti) implant with the calcium phosphate cement (CPC) and autograft prostheses by pull-out test and histological examination. Stems of sixty Ti cylinders were bilaterally inserted into femoral medullary canals in 30 rabbits at the 1st, 4th, 12th, 26th and 70th postoperative weeks. The bone autograft and CPC were filled into the pre-trimmed bone marrow cavity with a polymethyl methacrylate retarder in the distal end, and then a Ti cylinder was inserted into femurs. The CPC group was significantly (p<0.05) associated with a larger pull-out force at 4th (37%) and 12th (62%) weeks compared to the autograft group. The bone area and the bone-to-implant contact ratios of the CPC groups were significantly higher than that of the autograft groups at early healing stage. The histological exams suggest that the CPC enhanced the earlier bone formation around the implant at a period not longer than 12 weeks postoperation. We conclude that CPC graft has the higher ability to facilitate the osteointegration and stabilize the Ti implant at a relatively early stage than the autograft in vivo.     

Effects of fibre reinforcement on the mechanical properties of brushite cement

In this study the effect of structure and amount of polyglactin fibre incorporation into a brushite forming calcium phosphate cement system and the effect of mechanical compaction on the fibre modified system were investigated. In comparison the effect of resorbable polycaprolactone surface coating of cement specimens was investigated. The results showed that, apart from the mechanical properties of the reinforcing material, the structure of the incorporated fibres, regular or random, is crucial for the resulting flexural strength and modulus of elasticity. Fibre reinforcement could also be combined with mechanical compaction of the cement/fibre composite paste leading to a possible 7-fold increase in flexural strength or an almost 5-fold increase in modulus of elasticity. Reinforcement of the tensile surface of cement grafts may ultimately improve strength where required, especially in conjunction with bone fixation devices.     

Tendon-to-bone healing using an injectable calcium phosphate cement combined with bone xenograft/BMP composite

Injectable calcium phosphate cement (ICPC) has been applied to enhance the tendon-to-bone healing. However, its slow degradation delays the osteointegration of grafted tendon in bone tunnels. We therefore constructed a synthetic biomaterial of ICPC combined with recombined bone xenograft granules (RBX). In this study, the first stage study demonstrated that the ICPCB contained 3 mg BMPs (ICPCB-3) obtained a porous structure. More importantly, the values of ICPCB-3 were highest in cell proliferation, alkaline phosphatase (ALP) activity, expression of osteogenic genes, and newly ectopic bone-forming area (P < 0.05). Then, ICPCB-3 was used in an anterior cruciate ligament (ACL) reconstruction model. Ninety skeletal mature rabbits underwent bilateral ACL reconstructions and were assigned to 3 groups: control group, ICPC alone group, and ICPCB-3 group. Animals were sacrificed at 6, 12 and 24 weeks. The results showed compared with ICPC, ICPCB-3 composite markedly accelerated tendon-to-bone healing. In addition, little remnants were observed in ICPCB-3 group. Moreover, the maximum loads to failure of ICPCB-3 group was significantly higher than ICPC group at 24 weeks (P < 0.01). We conclude that the ICPCB composite, with a porous structure and better osteointegration effect, has direct clinical instruction to arthroscopic techniques of the ACL reconstruction.     

RhBMP-2-loaded calcium silicate/calcium phosphate cement scaffold with hierarchically porous structure for enhanced bone tissue regeneration

Calcium phosphate cement scaffold (CPC) has been widely used as bone graft substitutes, but undesirable osteoinductivity and slow degradability greatly hamper their clinic application. To address these problems, a recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded calcium silicate/calcium phosphate cement scaffold (CSPC) with hierarchical pores was developed in this study. The CSPC scaffold with both interconnected macropores on the order of 200–500 μm and micropores of 2–5 μm was synthesized from CPC and calcium silicate (CS) by a NaCl particulate-leaching method. In vitro cell culture with C2C12 model cells, in vivo ectopic bone formation and rabbit femur cavity defect repair were performed to evaluate the osteogeneic capacity of the CSPC/rhBMP-2 scaffold. CPC, CSPC and CPC/rhBMP-2 scaffolds were parallelly investigated for comparison. The results demonstrated that the hierarchical macro/microporous structure, whether in presence of CS or rhBMP-2, highly favored the adhesion of C2C12 cells and bone in-growth into the CPC-based scaffolds. But, in comparison to the CPC-based scaffolds with CS or rhBMP-2 alone, the CSPC/rhBMP-2 scaffold strongly promoted osteogenic differentiation in vitro and osteogenetic efficacy in vivo. Further studies demonstrated that Si ions derived from CSPC contributed mainly to maintain the conformation of rhBMP-2 and thus stimulate the synergistic action of CS and rhBMP-2 in osteogenic differentiation and osteoinductivity. Additionally, the incorporation of CS was also beneficial for the dissolution of the scaffold. Those results suggest that the CSPC has superior properties for incorporation of rhBMP-2 and our developed CSPC/rhBMP-2 scaffold have great potential for future use in bone tissue regeneration.     

新型大孔隙磷酸钙骨水泥作为骨组织工程支架的相关研究

目的 探讨新型大孔隙磷酸钙骨水泥(CPC)材料支架的细胞毒性和对细胞黏附、生长和增殖的影响.方法 通过添加甘露醇制孔剂和应用磷酸钠溶液作为CPC固化液的方法合成新型CPC材料.通过CCK8法检测细胞在新型CPC材料浸提液中的生长增殖情况;通过电子扫描电镜测试材料孔径和细胞在材料表面上黏附生长情况;应用力学三点弯曲实验测试新型CPC的生物力学性能.结果 新型CPC材料的孔径值达到(267.43±118.01)μm,孔隙率为(66.15±6.91)％.新型CPC材料的最大负荷、抗弯强度和坚韧度较传统CPC均增加了约1倍(P＜0.05).新型CPC材料浸提液与细胞共培养2、4、6、8d后CCK8法测试吸光度(OD)值与阴性对照组比较其差异无统计学意义(P＞0.05).结论 新型CPC材料具有强大的生物力学性能、大孔隙、高孔隙率和良好的生物相容性,有望成为理想的骨组织工程支架.     

Calcium phosphate cements for bone substitution: Chemistry,handling and mechanical properties

Since their initial formulation in the 1980s, calcium phosphate cements (CPCs) have been increasingly used as bone substitutes. This article provides an overview on the chemistry, kinetics of setting and handling properties (setting time, cohesion and injectability) of CPCs for bone substitution, with a focus on their mechanical properties. Many processing parameters, such as particle size, composition of cement reactants and additives, can be adjusted to control the setting process of CPCs, concomitantly influencing their handling and mechanical performance. Moreover, this review shows that, although the mechanical strength of CPCs is generally low, it is not a critical issue for their application for bone repair – an observation not often realized by researchers and clinicians. CPCs with compressive strengths comparable to those of cortical bones can be produced through densification and/or homogenization of the cement matrix. The real limitation for CPCs appears to be their low fracture toughness and poor mechanical reliability (Weibull modulus), which have so far been only rarely studied.     

Immersion behavior of gelatin-containing calcium phosphate cement

Calcium phosphate cements (CPCs) have many favorable properties that support their clinical use as bone defect repair. However, it is difficult to deliver to the required site and hard to compact adequately due to inherently low ductility of ceramics. The aim of this study focused on the effect of the gelatin content on properties of CPCs. The diametral tensile strength, morphology, and weight loss of gelatin cements were evaluated after immersion in physiological solution, in addition to setting time. The results indicated that the setting time significantly increased with increasing gelatin amount. The 2 wt.% gelatin could make CPCs attain the maximum strength value of 2.1 MPa at 15-day immersion, while 1.6 MPa for the cement without gelatin. It is concluded that the presence of gelatin improved mechanical properties of CPCs; in particular, 2 wt.% gelatin. CPCs containing 2 wt.% gelatin hardened in an acceptable time recommended for clinical applications.     

磷酸钙骨水泥强化椎弓根螺钉固定的周期抗屈试验研究

目的 本实验旨在从周期抗屈试验方面证实磷酸钙骨水泥对椎弓根螺钉固定的强化作用.方法 在一组Ⅰ级和Ⅱ级骨质疏松椎骨的一侧直接置入椎弓根螺钉作为对照,另一侧填入磷酸钙骨水泥后再置入椎弓根螺钉作强化固定,12h后进行周期抗屈试验.然后用磷酸钙骨水泥固定松动后的椎弓根螺钉并进行周期抗屈试验.在另一组Ⅲ级和Ⅳ级骨质疏松椎骨上重复以上试验步骤.结果 第一组椎骨对照侧的螺钉松动率为91.3%,强化侧为33.3%,两侧螺钉均松动椎骨的最大负荷中位数分别为75N和162.5N,两侧均未松动的9号椎体中,对照侧的螺钉位移1.942mm,强化侧仅为0.403mm,差别均有显著性意义.螺钉松动后重新固定,两侧的松动率均为41.7%,两侧螺钉均松动椎骨的最大负荷中位数分别为150N和175N,两侧均未松动的9号椎体中,螺钉位移均为0.411mm,与对照侧初始固定相比,均有显著性意义.第二组椎骨对照侧和强化侧的松动率均为100%.结论 磷酸钙骨水泥能强化椎弓根螺钉在Ⅰ级和Ⅱ级骨质疏松椎骨上的周期抗屈能力,但在Ⅲ级和Ⅳ级骨质疏松椎骨上无效果.     

壳聚糖对纳米碳管／磷酸钙骨水泥性能的影响

通过不同添加方式将壳聚糖与纳米碳管／磷酸钙骨水泥混合，研究壳聚糖对复合材料性能的影响。结果表明：壳聚糖与复合粉体充分混合后，再加入去离子水时，可以更好提高复合材料的弯曲强度，壳聚糖含量为0．5％时可以得到较短的凝固时间和较高的弯曲强度（12．99MPa）。     

Combined effect of strontium and pyrophosphate on the properties of brushite cements

In this study we report the synthesis of strontium-containing brushite cement with good cohesion and a diametral tensile strength (DTS) of 5 MPa. The cement powder, composed of β-tricalcium phosphate (β-TCP) and monocalcium phosphate, was adjusted by different concentrations of strontium and pyrophosphate ions. The cement liquid phase was 2 M phosphoric acid solution. The cement cohesion and mechanical properties were measured after being aged in water for 24 h at 37 °C. It was found that at low concentration both strontium and pyrophosphate ions inhibit the cement setting reaction. However, the final setting time was significantly reduced when SrCl₂ increased from 5 to 10 wt.% at pyrophosphate concentrations equal to or higher than 2.16 wt.%. The incorporation of strontium ions did not increase the DTS of brushite cements significantly. In contrast, the addition of pyrophosphate ions did increase the DTS of brushite cements significantly. When both ions were added simultaneously, the brushite cement with a Sr²⁺ content of 5 wt.% had the highest DTS value. Nevertheless, the DTS values of Sr-containing cements were significantly reduced if the pyrophosphate concentration was higher than 2.16 wt.%. The Sr²⁺ ions had a negative effect on brushite cement cohesion, although the solid weight loss started to decrease at Sr²⁺ concentrations higher than 5 wt.%.     

明胶联合壳聚糖纤维对磷酸钙骨水泥力学性能的影响

背景：已有多种纤维被用于提高磷酸钙骨水泥的强度及抗断裂性能。 目的：了解明胶联合壳聚糖纤维对磷酸钙骨水泥力学性能的影响,寻找较为合适的配比。 方法：采用2×4析因设计,将质量比为0(蒸馏水),5%的明胶,体积比为0,10%,30%和50%的壳聚糖纤维分别混入磷酸钙骨水泥,检测复合物的抗弯曲强度,扫描电子显微镜观察各组试样断口形态并进行电子能谱分析。 结果与结论：各明胶组间抗弯强度差异有非常显著性意义(P < 0.001);各体积比纤维间抗弯强度差异有非常显著性意义(P < 0.001),其中5%明胶和30%壳聚糖纤维构成的复合物抗弯曲强度最大,达 12.31 MPa。以蒸馏水为液相的磷酸钙骨水泥固化后,表面可见不规则颗粒,平均微孔直径小于5 μm,添加明胶后颗粒似乎黏在一起,微孔直径与前者相似,但是数目少于前者。磷酸钙骨水泥-5%明胶-30%纤维复合物的断口扫描可见拔出纤维的表面黏附有大量颗粒,磷酸钙骨水泥-蒸馏水-30%纤维复合物拔出纤维表面的颗粒明显减少。表明明胶与壳聚糖纤维可提高磷酸钙骨水泥的抗弯曲强度,5%明胶和30%壳聚糖纤维为这种增强模式较为合适的比例。     

3D生物描绘孔结构可控钙磷硅基骨修复支架的生物力学性能

目的设计和制备新型钙磷硅基骨修复支架,研究其在不同外力作用下体外生物力学性能。方法以自固化磷酸钙骨水泥(calcium phosphate cement,CPC)、介孔硅酸钙(mesporous calcium silicate,MCS)为原料,通过3D生物描绘技术构建孔径分别为350、500μm的MCS/CPC复合支架。采用扫描电镜观察支架表面形貌;分别通过万能力学试验机和动态力学分析仪,考察具有不同孔道结构MCS/CPC支架的抗压力学性能和不同频率动态周期性载荷作用下的力学性能。结果通过3D生物描绘技术能够实现对钙磷硅基骨修复支架内部孔道结构的可控制备。孔径为350μm的MCS/CPC支架具有较高的抗压力学强度[(9.80±0.39)MPa]和抗压模量[(132.50±4.30)MPa];此外,载荷频率在1~100 Hz范围内,孔径为350μm的支架具有较高的储能模量。结论通过3D生物描绘技术制备的孔径为350μm的MCS/CPC复合支架不仅具有规则的连通孔道,还具有较高的抗压力学性能,能在动态载荷作用下保持结构稳定,适合作为一种新型的骨缺损修复材料。     

Influence of the pore generator on the evolution of the mechanical properties and the porosity and interconnectivity of a calcium phosphate cement

Porosity and interconnectivity are important properties of calcium phosphate cements (CPCs) and bone-replacement materials. Porosity of CPCs can be achieved by adding polymeric biodegradable pore-generating particles (porogens), which can add porosity to the CPC and can also be used as a drug-delivery system. Porosity affects the mechanical properties of CPCs, and hence is of relevance for clinical application of these cements. The current study focused on the effect of combinations of polymeric mesoporous porogens on the properties of a CPC, such as specific surface area, porosity and interconnectivity and the development of mechanical properties. CPC powder was mixed with different amounts of PLGA porogens of various molecular weights and porogen sizes. The major factors affecting the properties of the CPC were related to the amount of porogen loaded and the porogen size; the molecular weight did not show a significant effect per se. A minimal porogen size of 40 μm in 30 wt.% seems to produce a CPC with mechanical properties, porosity and interconnectivity suitable for clinical applications. The properties studied here, and induced by the porogen and CPC, can be used as a guide to evoke a specific host-response to maintain CPC integrity and to generate an explicit bone ingrowth.     

磷酸钙人工骨(CPC)在颈前路椎间融合的临床应用

目的探讨磷酸钙人工骨(CPC)在颈椎前路椎间融合手术中的应用效果。方法2001年4月至2003年10月颈前路手术中应用磷酸钙人工骨栓椎间融合结合钛钢板固定治疗颈椎病17例,颈椎间盘突出症5例,颈椎外伤脱位2例,共24例35个节段。采用JOA评分评价神经功能,X线片判定融合效果。结果随访18±6.5个月,术后无感染,无过敏或毒性反应。JOA评分由术前9.28±2.15分增加到14.65±2.18分(P<0.001)。术后X线片未见CPC骨栓塌陷或移位,钛板和螺钉无松动及折断。术后16.5±6.8个月均获得椎间融合。结论颈椎前路椎间融合手术应用磷酸钙人工骨替代自体骨,经济、安全、简便、效果可靠。